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Re: Electrolytic capacitor info for you DIY'ers

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  • dtproff
    I will add a bit more to the capacitor topic below. I am a power supply engineer and swollen capacitors are aren t always the fault of the manufacturer. The
    Message 1 of 3 , Oct 21, 2008
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      I will add a bit more to the capacitor topic below.

      I am a power supply engineer and swollen capacitors are aren't always
      the fault of the manufacturer. The biggest problem I have found has
      been the misuse of an electrolytic by the design engineer. Ususally
      it is the result of the ripple current in the capacitor being too
      high. This causes the internal temperature to rise inside the cap.

      Check the spec on the capacitor then use a current probe to verify
      the ripple current into the cap. Pay attention to the frequency that
      the capacitor is seeing. If it is to large then add a film cap across
      it and then check the leg on the cap again. The film cap will have a
      lower ESR and shunt some of the current off the Aluminum
      Electrolytic. Be sure and test the leg of each capacitor and don't
      exceed the manufacturers published spec.

      Tony

      --- In dallasaudioclub@yahoogroups.com, Paul Stewart
      <musicman32150@...> wrote:
      >
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      > Good info!
      >
      > To: dallasaudioclub@yahoogroups.com
      > From: jim@...
      > Date: Tue, 22 Jul 2008 12:13:47 +0000
      > Subject: [dallasaudioclub] Electrolytic capacitor info for you
      DIY'ers
      >
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      > Hi guys,
      >
      > Below is a copy and paste post from my FM tuner group. OH LOOK!
      My
      >
      > favorite brand,Panasonic,was not part of the problem.
      >
      > 8:-) jim...
      >
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      > Re: Upgrade or Replace Caps
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      > Yes Tom,
      >
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      > Right on target.
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      > That bad formula made their way into just about every Taiwanese,
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      > Chinese, and Korean electrolytic cap manufacturer.
      >
      > Very quickly, the cap manufacturers who chased after the cheap
      >
      > formula became identified, as the first products to fail were
      >
      > computer motherboards, requiring stable capacitors.
      >
      > Those computer motherboards using (good for the Japanese - they
      still
      >
      > have a conscience about quality) Panasonic, United ChemiCon or
      >
      > Nichicon Capacitors were remarkably trouble-free. It became
      perfectly
      >
      > obvious which cap manufacturers were NOT using the bad formula,
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      > http://www.pcstats.com/articleview.cfm?articleID=195
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      > http://www.siliconchip.com.au/cms/A_30328/article.html
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      > Even today, after a couple of years, since the bad formula problem
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      > was supposed to have passed, we still see Luxon, Rubycon, and many
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      > other types of caps, swollen, and leaking electrolyte.
      >
      >
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      > For that reason alone, we use only Panasonic, Nichicon or United
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      > ChemiCon electrolytics.
      >
      > BTW, Vishay's electrolytic caps are just too expensive to find
      their
      >
      > way into the computer motherboard market, but rest assured that
      their
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      > caps (Roderstein, Sprague, BCComponents, Philips) are probably the
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      > most reliable and longest life caps available today.
      >
      >
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      > And we never touch NOS (New Old Stock) capacitors.
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      > I personally don't like Tantalums, because when they fail, they
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      > SHORT, with disastrous results for hard-to-find tubes, and
      >
      > semiconductors.
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      > All other capacitors, when they fail, (barring any extraneous
      >
      > circumstances) they will fail OPEN!
      >
      >
      >
      > But Tantalums are DIRT CHEAP, so you will find them in many
      >
      > applications today, where the emphasis is on profits, and not
      quality.
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      >
      > We had a well-known manufacturer who was very keen for us to start
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      > using their Tantalums.
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      > We finally gave in and said, OK, send us 100 samples for
      evaluation.
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      > After testing, it turned out that although all 100 were within the
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      > specified 5% capacitance tolerance, only 6 of the 100 were within
      ESR
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      > limits. 94 failed the tolerance test.
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      > And that was supposed to be from a cherry-picked batch, in order to
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      > convince us to buy production quantities! We gently informed the
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      > manufacturer that we wouldn't be buying their tantalums.
      >
      >
      >
      > Anyway, you can draw your own conclusions as to why today's
      >
      > electronic products have such a short lifetime.
      >
      >
      >
      > I prefer Wima MKS2 MPE capacitors, instead of Tantalums - in the
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      > order of x100's more stable, and compact footprints with up to 15uF
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      > currently available - in fact, they are probably the most compact
      >
      > Metallized Polyester caps in the world today. They (MPR and MPE)
      are
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      > also non-polar, so they substitute perfectly for any polarized cap.
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      >
      >
      > And I'll add to Tom's advice about the best place to start being
      the
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      > power supply - absolutely! The second place to concentrate is the
      >
      > audio path - that's where you'll HEAR the difference.
      >
      >
      >
      > Menahem Yachad
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      > Israel
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      > _________________________________________________________________
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